Predicting hematological toxicity (myelosuppression) of cytotoxic drug therapy from in vitro tests

Abstract

Several clinical oncology units are studying the roles of in vitro hematotoxicology in phase I evaluations. At the same time, the European Center for the Validation of Alternative Methods (ECVAM) is supporting a validation study of the CFU-GM assay. It is important that these activities be coordinated so that high performance, optimized technical protocols are used for prospective and retrospective clinical evaluations. The EROTC, the NCI and ECVAM could provide support for these coordinated efforts. There is an opportunity for medical oncologists involved in early clinical trials to participate in the evaluation of in vitro tests and their clinical application . Fundamental to acceptance of these assays by oncologists and regulatory scientists, they must predict clinical outcome for myelosuppressive agents and then improve phase I design and performance. These achievements would justify more aggressive dose escalation schemes using guidance from in vitro studies without compromising patient safety. Success in predicting neutropenia might also stimulate the research required to understand how to predict other hematologic toxicities, such as a thrombocytopenia. The complexity of a validation study in hematotoxicology is that it seeks to predict the level of exposure that causes neutropenia, in contrast to other validation studies that have sought to classify a xenobiotic as toxic or not. It may be that the clinical relevance of a new assay is not just a yes-no answer. This important distinction came from the realization that the xenobiotic tolerance in other organ systems of the body must be the same or greater than marrow in order for myelosuppression to be a clinical consequence of exposure. Pharmacological principles of system exposure and toxicity that are integrated into the prediction model provide the links to clinical oncology. It is also important to anticipate future applications of in vitro hematotoxicology. If the maximum tolerated level of drug exposure for human hematopoietic cells can be predicted, then in vitro hematotoxicology could play an important role in new drug discovery. One concept involves screening for compounds that show efficacy at the IC level that predicts maximum tolerated exposure levels in the human. 'Therapeutic index based' drug discovery has been applied to the tallimustine family with some success.

Induction of apoptosis in retinoid-refractory acute myelogenous leukemia by a novel AHPN analog

“…These data would strongly predict that 3-Cl-AHPC should be well tolerated in humans and display preferential toxicity in vivo against leukemia cells and significantly less toxicity to normal marrow. 59 Exposure of M07e and patient leukemic cells to 3-Cl-AHPC resulted in apoptosis, as documented by a number of parameters. Staining of the cells with acridine orange following incubation with 3-Cl-AHPC revealed an intact plasma membrane but also nuclear fragmentation, which are characteristics associated with the process of apoptosis.…”

Integration of in vivo and in vitro approaches to characterize the toxicity of Antalarmin, a corticotropin-releasing hormone receptor antagonist

“…Colony counts (normalized as a percentage of control) at each concentration were then plotted to generate the concentrationresponse curve. As previously reported (Erickson-Miller et al, 1997;Parchment et al, 1994Parchment et al, , 1998Pessina et al, 2003), the endpoint of the assay for quantifying inter-species differences in susceptibility to drug toxicity is the IC 90 , which is the concentration that inhibits colony formation by 90%. IC 90 values were calculated from log-linear regression on concentrationresponse between the flanking data points on either side of the 90% inhibition level.…”

“…Dog bone marrow aspirates were collected sterilely from the iliac crest or femoral canal of donor beagle dogs into a 50 ml syringe containing sodium heparin and gentamicin to final concentrations of 10 IU/ml and 20 μg/ml, respectively. CFU-GM assays were performed as previously described (Erickson-Miller et al, 1997;Parchment, 1998;Parchment et al, 1993Parchment et al, , 1994Parchment et al, , 1998, except that species-specific recombinant GM-CSF was used as the sole cytokine in each culture.…”

Stem cells in myelotoxicity

“…Parchment et al (1998) proposed different models for predicting human MTDs taking into account murine and human IC 90 values and murine MTD. This model has been tested for food contaminants (Parent-Massin and and validated during the prevalidation phase of the ECVAM program for 10 drugs .…”